This invention relates in general to electrostatography and, more specifically, to a system for removing coating material from an end of a drum.
In electrostatography, and particularly in electrophotography, coated substrates such as cylindrical photoreceptor drums (photoreceptors) are commonly used in copier, duplicator, facsimile and multifunctional machines. Photoreceptor embodiments include at least one coating of photosensitive material comprising film forming polymer material, which can be formed on the photoreceptor by known techniques such as immersion or dip coating.
The peripheral ends of a coated photoreceptor are often used to engage members such as spacers, rollers, seals, developer housings, grounding devices and the like. If these members ride on a coated area of the drum, the coating material is rubbed off and the resulting debris can contaminate various components in the machine such as the cleaning system and any optical exposure systems employed in the machine. Also, the coating can interfere with devices that are designed to electrically ground the drum by contacting the outer surface at one end of the drum. Moreover, if the coating thickness is irregular because of poor removal techniques, spacing devices riding on the outside surface of the drum cannot maintain precise spacing between the drum and critical subsystems such as charging, developing, cleaning or other subsystems. Further, if coating material is present in the interior of the drums adjacent the ends of the drum, insertion of supporting end caps may be prevented or hindered. Also, uneven coating deposits in the interior of the drums can cause misalignment of the end caps which, in turn, can cause the drum to wobble during image cycling. The uncoated region at the end of the drum is also necessary to prevent delaminating or cracking of the organic layers at the base of the photoreceptor when the photoreceptor is cycled in an imaging machine. Thus, specified areas at both the outer and inner peripheral ends of a photoreceptor must be free of coating material.
The top of the drum may be maintained free of deposited coating by not immersing a small portion of the upper end of the drum into the coating solution. More specifically, the upper end of the photoreceptor drum can be kept free of coating material by orienting the drum vertically and dipping the drum into a bath of coating material to a predetermined depth which avoids complete immersion of the drum. However, the coating formed over the lower end of the photoreceptor must still be removed or prevented from depositing during dip coating. There are many methods and techniques for accomplishing this. One technique for preventing coatings from depositing is by masking the lower end of the drum prior to dip coating. This technique is time consuming and requires excessive handling. Systems for removing deposited coatings include, for example, laser ablation, mechanically wiping the lower end with blades or brushes and/or by applying solvents to it.
In the laser ablation coating removal technique, a predetermined portion of a coating on a photoreceptor is treated to remove at least part of the coating by directing high energy radiation such as a laser beam and a number of fluid jets at the coating to remove at least part of the coating. This process is often referred to as xe2x80x9claser ablation.xe2x80x9d The laser ablation process functions to effectively remove at least part of a predetermined portion of a coating without the need for chemical or mechanical treatments. During laser ablation, the coated substrate is rotated at high speeds. However, a problem is that a rotating cylindrical substrate which is supported only at one end, i.e., a cantilevered state, may sway when the rotation speed is high and/or when the substrate has a relatively small diameter. Swaying of the substrate during for example laser ablation may affect the precision of the ablation process. The laser ablation process is described in detail in U.S. Pat. No. 5,418,349, U.S. Pat. No. 5,424,508 and U.S. Pat. No. 5,628,918, the entire disclosures thereof being incorporated herein by reference. Supplemental devices to reduce drum sway during laser ablation is described in U.S. Pat. No. 5,628,918, the entire disclosure thereof being incorporated herein by reference. Laser ablation systems are complex, expensive and occupy valuable manufacturing space.
Another coating removal method involves using a wiper blade or brush to wipe off the bottom portion of each drum with solvent, to remove the organic polymer films in the intended uncoated region. One technique involves lowering the drum onto a sponge spindle to steady the end of the drum and thereafter, wipe the bottom outside edge of the drum with a flexible wiper blade. This blade wiping system utilizes tapered elastomeric rollers. Each roller is mounted on one end of an arm which has a center pivot point. The other end of the arm carries a wiping blade. As a drum is lowered, the end of the drum engages the tapered end of each roller causing it to offset and move the arm which, in turn, causes the blade to wipe the coating material from the outer surface of one end of the lowered photoreceptor. This method performs well with photoreceptors which require a large coating-free circumferential strip having, for example, a width of 9 millimeters. However, for photoreceptors requiring a relatively small coating-free circumferential strip having, for example, a width of 4 millimeters, consistent, reliable wiping cannot be achieved. Part of this reduction in quality for narrow coating-free circumferential strips is due to the drum wobbling during coating removal, misalignment of the wiper blades on the surface of the drum, and loss of elastomeric roller material as the drum is lowered into contact with the tapered end of the elastomeric rollers. Loss of the material from the rollers causes the rollers to roll erratically rather than smoothly. Moreover, loss of material from the rollers aggravates precise alignment of the drum and blades for cleaning. Also, during lowering, the drum will occasionally contact the blades and dislodge them from alignment. If the rollers are biased against the drum with too much pressure, the drum is pulled off of the mandrel when the mandrel is retracted to remove the drum from the cleaning station. Moreover, the nicked rollers produce debris that deposit on the wiped surface of the bottom of the drum. Replacement and realignment of the rollers requires downtime during which production must be stopped. Further, solvent used to carry away removed coating material often rides up on the rollers and form unwanted coating deposits on the cleaned bottom surface of the drum. Thus, quality control is difficult to maintain. Further, these cleaning systems require frequent replacement of parts, along with attendant downtime. Even with optimization of the bottom edge wipe with wiper blades the reject rate can be as high as 20 to 25 percent.
Another technique for cleaning drums is to utilize brushes with solvents. Because the bristles of the brush tend to flick coating material and solvent during the cleaning operation, the coating material in the imaging area can receive unwanted solvent and/or coating material from the brushes during the cleaning operation. These cleaning devices become less efficient and reliable when the cleaned strip at the end of the drum has a very small width, for example, about 4 mm wide.
Thus, each coating prevention or removal technique has its advantages and disadvantages. In all cases, there should be little or no residual organic polymer in the bottom uncoated area or it is considered defective for the reasons described above. To prevent defective photoreceptors from getting to the customers, it is necessary to carefully inspect each photoreceptor to detect these defects during the manufacturing process. Therefore, a very large amount of time and expense is required to weed out otherwise acceptable photoreceptors.
U.S. Pat. No. 5,418,349 issued to Swain et al on May 23, 1995xe2x80x94A process is disclosed for treating a coated substrate to reduce the thickness of the coating involves directing a laser beam at a predetermined surface portion of the substrate to remove part of the coating. The process can be used to treat a coated photoreceptor to precisely reduce the thickness of the coating in a predetermined region.
U.S. Pat. No. 5,424,508 issued to Swain et al on Jun. 13, 1995xe2x80x94A system is disclosed for removing a band of coating material from a first end of a coated cylinder having a second opposite end including ablating the band of coating material with a laser beam and directing an annular curtain of compressed fluid against the band in a direction away from the second opposite end to create an air curtain along the outer surface of the cylinder in a direction from the second opposite end toward the band and the first end.
U.S. Pat. No. 5,628,918 issued to Mastalski on May 13, 1997xe2x80x94A method is disclosed comprising: (a) rotating a hollow cylindrical substrate having a coating thereon; (b) employing a gas bearing around the circumference of the rotating substrate along a portion of the length of the substrate to provide support to the substrate during its rotation; and (c) removing a portion of the coating.
U.S. Pat. No. 5,670,291 issued to Ward et al on Sep. 23, 1997xe2x80x94A process is disclosed for fabricating an electrophotographic imaging member including providing a substrate coated with at least one photoconductive layer, applying a coating composition to the photoconductive layer by dip coating to form a wet layer, the coating composition comprising finely divided amorphous silica particles, a dihydroxy amine charge transport material, an aryl charge transport material that is different from the dihydroxy amine charge transport material, a crosslinkable polyamide containing methoxy groups attached to amide nitrogen atoms and a crosslinking catalyst, at least one solvent for the hydroxy amine charge transport material, aryl charge transport material that is different from the dihydroxy amine charge transport material and the crosslinkable polyamide, and heating the wet layer to crosslink the polyamide and remove the solvent to form a dry layer in which the dihydroxy amine charge transport material and the aryl charge transport material are molecularly dispersed in a crosslinked polyamide matrix.
U.S. Pat. No. 5,893,568 issued to Swain et al on Apr. 13, 1999xe2x80x94A device is disclosed for supporting a hollow substrate having two open ends in an aligned orientation, wherein one end of the substrate is engageable with a chuck assembly, including: (a) a base for contacting the other end of the substrate; (b) a post coupled to the base, wherein a section of the post is positioned within the substrate, thereby defining a substrate disposed post section; and (c) a spring apparatus coupled to the substrate disposed post section, wherein the spring apparatus is disposed within the substrate and contacts the substrate interior surface, wherein the spring apparatus is compressed by the substrate during misalignment of the substrate with the device and the compressed spring apparatus springs back to push the substrate to the aligned orientation with the device.
It is, therefore, an object of the present invention to provide an improved edge cleaning system for electrostatographic imaging drums.
It is another object of the present invention to provide an improved edge cleaning system for electrostatographic imaging drums.
It is still another object of the present invention to provide an improved edge cleaning system for electrostatographic imaging drums that reliably removes circumferential strips of coating material having a narrow width as well as those having a wide width.
It is yet another object of the present invention to provide an improved edge cleaning system for electrostatographic imaging drums having excellent wiping capabilities.
It is another object of the present invention to provide an improved edge cleaning system for electrostatographic imaging drums which forms high quality cleaned circumferential strips.
It is still another object of the present invention to provide an improved edge cleaning system for electrostatographic imaging drums that is easier to maintain and reduces maintenance.
It is yet another object of the present invention to provide an improved edge cleaning system for electrostatographic imaging drums which is less complex.
It is another object of the present invention to provide an improved edge cleaning system for electrostatographic imaging drums which avoids damage during cleaning cycles.
It is still another object of the present invention to provide an improved edge cleaning system for electrostatographic imaging drums which simultaneously wipes both the inside and outside of the bottom edge of a coated photoreceptor.
It is yet another object of the present invention to provide an improved edge cleaning system for electrostatographic imaging drums which is easier to set up and maintain.
The foregoing objects and others are accomplished in accordance with this invention by providing a process comprising
providing a hollow imaging drum having
a first end, a second end,
an outside surface,
an inside surface and
coating material on both the inside surface and the outside surface at at least the first end,
simultaneously contacting the coating material on both the inside surface and the outside surface at the first end of the drum with resilient foam material,
flowing liquid solvent for the coating material to the foam material where the foam material contacts the first end of the drum, the foam material being insoluble in the flowing solvent,
producing relative movement between the foam material and the drum to
simultaneously wipe both the inside surface and the outside surface of the first end of the drum with the foam material and solvent material and
simultaneously remove coating material from the inside surface and the outside surface of the first end of the drum, and
flowing the solvent away from the drum to carry away coating material removed from the inside surface and the outside surface of the first end of the drum.